electrical panel question

I have a 35 year old 100 amp service. I had my old furnance and AC replaced
with a geothermel unit about a year ago. When they did the install they
used all of the remaining free slots for new breakers. The issue is when
the unit comes on the lights dim for a second. Will upgrading to a 200 amp
service prevent the lights from dimming?
Thanks,

Heck wether or not it fixes dimming a new service is a excellent thing
after all these years. Updates grounding and all the rest thats changed
in over 30 years, good investment for your future too.
someday you may want to sell the home

If his house only draws 75 amps(number not important, just an
example), then a service upgrade is a waste of money. If you wan to
upgrade grounding, get a ground rod, length of wire, and pipe clamps
to bond house pipes, and save money live with it, and only upgrade
when you need to.
tom

Impossible to say.
I don't know anything about geothermal units, but they couldn't possibly
take anywhere near 100a even at startup.
If it dims your lights and electric stove and electric water heater are on,
then yes, a larger service will likely help you. Or try not to run so many
heavier users at once.
If it dims your lights when nothing is on but a few lights, then no, it
probably won't help; the problem lies elsewhere.
Also, it would be nice to know current your geothermal unit draws.

In AC mode it is supposed to take between 25-30 amps. 1 20amp circuit is
for the circulation pump. 1 60 amp circuit is for the unit itself, the
blower, and the electric backup heater. The lights only dim with the unit
turns on. After a second the lights return to normal. It just gets a
little annoying when you are reading a book and the lights dims.
I do not have an electric water heater. I don't have any really heavy users
of electricity. I typically only use my PC, frig, TV, sat receiver,
microwave, and a few lights. They are all on different circuits and only
sometimes used all at the same time. I really don't use a lot of
electricity so I don't what is causing the lights to dim. I blame the
geothermal unit because it happens when the unit turns on. Any suggestions
as to what it could be?
Thanks,

Can you get ahold of an ampmeter? If you measure how many amps are being
used on each leg before and during startup, you will have an idea where to
go.
It is hard to know otherwise. 30a is a lot of current on a 100a service,
but not if nothing else is using current. But it might have much higher
startup current; no way to know without testing or asking the manufacturer.
My refrigerator uses 16a to start, but only 1a to run. On the other hand,
your backup heater probably uses the same to startup as to run.

replaced
amp
As another poster pointed out, a service upgrade is a good idea. However I
would call the power company and tell them what has been happening. Suggest
that the transformer feeding your house may be too small. If they decide to
upgrade the transformer and it corrects the problem, then you may be set for
awhile and it would not have cost you anything (I presume). If upgrading
the transformer does not correct the problem, than you should get some
estimates on a service upgrade.

Depends on where the voltage drop is occuring. If it occurs inside your
house, then you need to use bigger wires. If it occurs outside your house,
then you call the power company.
To determine this, measure the voltage in your main panel while the dimming
is happening. If the voltage in the panel dropped alot (say more than 10V),
then call the power company. If the voltage in the panel doesn't drop much,
then the voltage drop is happening inside your house.
10V is something I pull off the top of my head. I'm sure NEC has a
recommended voltage drop limit somewhere.

I am not an electrician, but are you really concerned about dimming
for a second, which seems trivial no matter how often it happens each
day, or about something else? I suspect your worried that something
worse is happening somewhere, and afaik, nothing is.

good old fashioned incandescent light bulbs are what I use. I am looking to
switch some of my frequently used bulbs to LED bulbs but finding a LED bulb
that can put out the same lumens as a 75 watt incandescent bulb and fit into
a table lamp is hard and the one found (puts out the lumens, but would not
fit in the lamp) is expensive. I hate flurosecent bulbs. One they hum.
With a lamp by my bed and me reading a book I can hear the hum and I don't
like it. Two they contain mercury. While I am not a tree hugging hippie, I
don't go out of my way to hurt the environment. Where I live no one
recycles mercury. I have an old mercury thermostat that I no longer use and
want to get rid of, but I don't know where to dispose of it properly.
Thanks,

LED replacement bulbs are a very poor choice at present. Perhaps in a
few more years, but not right now, the cost : benefit ratio is crap
currently.

You have apparently not tried any of the CF lamps. They *do not* hum,
they have high frequency electronic ballasts. The fluorescent lamps that
hummed were the very old ones with magnetic ballasts that are rarely
used anywhere these days. Get a CF and try it, they use 25% of the
electricity for the same light output as the incandescent.

They contain very little mercury, and what little they do contain they
more than offset over their 7+ year life span with the mercury emissions
from coal power plants that they eliminate by using 1/4 of the power
your incandescents do.
As for your dimming lights, the best thing to do is insure that all
connections in your panel and meter socket are properly tightened. If
the dimming is still an issue get an amp probe that has peak hold
capability and see what the heat pump is really pulling on startup. It
would also help to know how long your service drop is from the
transformer to your house.
Pete C.

I have come to the same conclusion about LED bulbs. They are just too
expensive at this point. I hope they come down in price shortly. From what
I have read they use less power than a CF bulb.
I have not tried CF bulbs in about 3 years. The one I purchased hummed
loudly. I know about the switch from magnetic ballasts to electronic
ballasts but the packages I have looked at never SAY what type of ballast
they have in it. I would like to try one, but I fear I might find the one
CF that still uses magnetic ballasts. Do all CF use electronic ballasts
these days?
From the pole to the meter it is approximately 120 feet. From the meter to
panel it is about 3 feet. The current power feed is overhead. If I upgrade
to a 200 amp service I would have them bury the cable. It would make the
house look nicer and I would not have to worry about the huge icicles that
form on the cable in the winter.
Thanks,

That's kind of sweet that you are still naive enough to believe they
last 7+ years just because the package says so. They often burn out
after only a few hours; then you are stuck paying another $1 disposal
fee to throw away your $3 bulb because it has mercury in it.
I like the concept of compact fluorescents, but some of them are junk,
and you really can't tell the junk from the good ones by looking at the
label (or the brand name.)
Best regards,
Bob

I've been using quite a few of them for 8 or 9 years and I've replaced
about 2 in that time and those were ones that are on 24x7. Every single
CF I've used has lasted at least 4 years for the 24x7 ones and the low
use ones are still going.

What hell hole are you living in? I don't have to pay any fees to
dispose of my used CFs or the 4' T8s in my shop.

I've used a number of brands, including the Home Depot CE house brand
and have had no issues with any of them. Are you sure you aren't putting
them in fixtures with dimmers (unless they're dimmable rated) or in non
ventilated fixtures (unless rated)? That can kill them quickly.
Pete C.

I am not looking at your panel, so this pure option, not a how-to. :D
I have a 200 amp service, and when my ac comes on, I get dimmed
lights.
Might be something you just have to live with. If you are concerned,
get someone to check your panel bus voltages, during a start/run/stop
phases. Becareful, if any electrician tells you that you have to
upgrade, then ask them for a "service calc" to prove it. If they look
at you weird, kick the cheat out. ;)
As for your lack of spaces, well if you don't want to add another
circuit, you should never have any problems with that. If want to add
another circuit, you will have to speak with an electrician. If you
still don't need an upgrade, with new service calc, then a subpanel
and moving two old circuits over to the new sub, with the new circuit,
might be the cheaper results.
tom

my comments about upgrading, with a 35 year old panel you get all new
breakers, they can go bad overtime. plus arc fault breakers for
bedrooms and GFCI kitchens and baths. plus the panel is mazed out. come
time to sell the home all these issues equal less money... let alone
upgrading to code for grounding.
35 years is a long time and electrical use continues to grow

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